The disclosure relates to turbofan engines. More particularly, the disclosure relates to fan blade mounting.
An exemplary turbofan engine includes one or more blade stages driven directly or indirectly by a low pressure turbine (LPT) of the engine. In an exemplary blade stage, the circumferential array of blades are mounted to a disk or other hub structure. Exemplary blades include a dovetail attachment root which is received in a dovetail slot in the hub. The exemplary slot and root have a base and have a first side and a second side extending radially outward from the base and generally converging toward the outer diameter (OD) perimeter of the hub. There may a rounded interface between the slot and the hub (OD) surface. The slots may be longitudinal or off-longitudinal at an acute angle and may be straight or have a curvature.
Exemplary blades comprise at least a substrate formed of a titanium alloy, an aluminum alloy, a composite or combination. Exemplary hubs are of titanium alloy or aluminum alloy. Portions of the blades may bear coatings for one or more purposes (e.g., corrosion protection, erosion protection, foreign object damage, or even abrasive coatings at blade tips). To protect the interface between the root and the slot, it is known to use wear pads along the sides of the root. The exemplary wear pads are formed of sheet stock of non-metallic material (e.g., polymeric fabric or other fabric material). Exemplary fabric material is VESPEL ASB polyimide, E. I. du Pont de Nemours and Company, Wilmington, Del.